One Stage Atmospheric Pressure Thermo-Catalytic Plasma Gasification and Vitrification of Organic Material such as Biomass for the Production of Renewable Energy

ABSTRACT

An apparatus for one stage thermo-catalytic plasma gasification and vitrification of organic material comprising: a generally funnel-shaped reactor having an upper section and a lower section, the lower section comprising a first, wider portion connected by a frustoconical transition to a second, narrower portion, and being suitable to receive a catalyst bed, and the upper section having at least one gas exhaust port; a plurality of inlets for the material from a plurality of directions located at the upper part of the lower section for introducing material into the upper portion of the lower section; a gas inlet system disposed around the lower section to provide gas into the lower section through one or more intake ports in the lower section; and a plurality of plasma arc torches mounted in the lower section to heat the catalyst bed and material, along with a method for plasma treatment of biomass.

TECHNICAL FIELD

The present disclosure relates to an apparatus and process to manufacture a synthetic gas (syngas) for production of renewable energy, including electricity, transportation liquid fuels, steam, etc. from organic material, especially biomass sources of fuel such as waste, including municipal solid waste (MSW) and industrial waste, agriculture waste, etc. by means of gasification utilizing non-transferred plasma arc heating technology.

BACKGROUND ART

Studies from the UN, IPCC, EPA and other public organizations confirm that energy requirement is becoming a serious and crucial issue worldwide because consumption is increasing at alarming rates with increasing population and industrialization. Unfortunately most of the world's energy is produced from the combustion of coal or other fossil fuels, which has been proven to result in the alarming rise of green house gases and subsequent global warming. Combined with the rapid growth and energy demand of large populous countries such as China and India, this has resulted in sharp rises of oil and gases to record levels. Additionally, as most of the oil and gases are located in geopolitical unstable countries, there is a further incentive for the US and most western countries to exploit alternative energy sources from indigenous feedstocks for energy security reasons.

The clear and undisputable solution to all of the above issues is the development of green and alternative energy sources. This has resulted in the rapid growth of wind and solar energy worldwide; however, these two energy sources are intermittent in nature as well as geographically and weather dependent, but most importantly, they do not address the transportation fuel issue. The only source of renewable energy that can provide reliable energy, whether in the form of electricity or liquid fuel, is biomass.

Worldwide, more and more biomass, whether municipal or industrial biomass, agricultural leftovers, biomass, etc., are either dumped or remain unexploited, releasing methane in the atmosphere. The impact of methane is estimated to be twenty-one times more harmful to the environment than carbon dioxide. Furthermore, due to poor biomass management methods in the past decades along with polluting energy production technologies such as burning coal, there are continual increases in carbon dioxide and green house gases emission resulting in worsening global life cycle assessment.

Biomass is also being burned in common incinerators, creating emissions of pollutants, including carcinogenic materials such as semi-volatile organic compounds (SVOCs), dioxins, furans, etc., that are products of low temperature combustion.

The need for an apparatus and process for dispensing with various forms of biomass and other organic materials as well as providing a source of readily renewable electrical energy has been met in part by the apparatus and process disclosed and claimed in U.S. Pat. Nos. 5,544,597 and 5,634,414 issued to Camacho and assigned to Solena Fuels Corporation, the assignee of the present application. These patents disclose a system in which biomass or other organic material is compacted to remove air and delivered in successive quantities to a reactor having a hearth. A plasma torch is then used as a heat source to pyrolyze organic components, while inorganic components are removed as vitrified slag.

More recently, improvement of the apparatus and process of the above patents for the pyrolysis, gasification and vitrification of organic material, such as biomass has been disclosed in U.S. Pat. No. 6,987,792 to Do et al and also assigned to Solena Fuels Corporation. U.S. Pat. No. 6,987,792 provides an improved material feeding system in order to enhance further the efficiency of the process as well as to increase the flexibility of the system, increase the ease of use of the material handling system, and allow the gasifier to receive a more diverse and varied material stream.

The apparatus and process of U.S. Pat. No. 6,987,792 ensures that high temperature is maintained in the bed zone through the use of plasma torches in conjunction with a catalyst bed. Additionally, several rings of tuyeres have been designed in different elevations of the bed to inject, for example, oxygen enriched air from the sides of the rector to its center in order to maintain (i) high temperature and (ii) an efficient and complete gasification condition along the overall cross sections of the gasifier, while observing sub-stoichiometric conditions.

This process produces a syngas containing mainly hydrogen and carbon monoxide, which exists at the top of the gasifier at an elevated temperature. Under the conditions typically practiced, the syngas can be reliably produced from various organic feedstocks and is free of unsaturated hydrocarbons. This biomass derived syngas is then used as a fuel gas replacement to natural gas for the production of clean renewable energy in the form of heat, steam or electricity.

Notwithstanding the improvements provided by the inventions in U.S. Pat. No. 6,987,792, room for further improvement still remained. For instance, it has been observed that the refractory lining protecting the funnel-shape upper section shell has shorter lifetime expectancy due to the continuous abrasion of organic feed material that is rolling on the refractory lining in the vicinity of 14 shown in FIG. 1.

SUMMARY OF DISCLOSURE

The present disclosure addresses the above problem concerning the refractory lining. In particular, according to the present disclosure, the biomass or other organic feed material is introduced into the apparatus at an upper part of the lower section of the apparatus.

An aspect of the present disclosure is concerned with apparatus for plasma gasification and vitrification of biomass or other organic sources comprising a generally funnel-shaped reactor having an upper section and a lower section. The lower section comprises a first, wider portion connected by a frustoconical transition to a second, narrower portion, and is suitable or capable to receive a catalyst bed. The upper section has at least one gas exhaust port. A plurality of inlets for the biomass or other organic feedstock is located at an upper part of the lower section above the top of the catalyst bed for introducing the biomass or other organic feedstock into the upper part of the lower section from a plurality of directions. A gas inlet system is disposed around the lower section to provide gas into the lower section through one or more intake ports in the lower section. A plurality of plasma arc torches is mounted in the lower section to heat the catalyst bed and the material being processed.

Another aspect of the present disclosure relates to a method for the conversion of material comprising waste, biomass or other carbonaceous material by plasma gasification and vitrification. The method comprises providing a catalyst bed in a lower section of a reactor; providing one or more successive quantities of the material being processed from a plurality of directions into an upper part of the lower section of the reactor above a catalyst bed, the upper part having at least one gas exhaust port connected to a fan, the material being processed forming a bed atop the catalyst bed; heating the catalyst bed and the material bed using a plurality of plasma arc torches mounted in the lower section; and introducing into the lower section a gaseous oxidant.

Still other objects and advantages of the present disclosure will become readily apparent by those skilled in the art from the following detailed description, wherein it is shown and described preferred embodiments, simply by way of illustration of the best mode contemplated. As will be realized the disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, without departing from the disclosure. Accordingly, the description is to be regarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation view of a prior art apparatus.

FIG. 2 is an elevation view of a gasifier used with an embodiment of the present disclosure.

FIG. 3 is a graph of pressure drop versus diameter size of the feedstock employed according to the prevent disclosure.

FIG. 4 is an elevation partial view of a gasifier used with an embodiment of the present disclosure illustrating representative pressure and temperature sensors.

FIGS. 5A-5C are cross-sectional views of FIG. 4 illustrating location of representative pressure and temperature sensors.

DESCRIPTION OF BEST AND VARIOUS MODES FOR CARRYING OUT DISCLOSURE

Details of the disclosure will now be presented. For ease of reference, this description will discuss the material to be handled by this apparatus and process as biomass, since the use of such material provides the benefits both of reducing green house gases and carbon footprint by producing a biomass derived syngas (Bio-syngas) for the production of electricity, steam, transportation liquid fuels and the like. However, this apparatus and process can work with any organic material.

Gasifier

A typical one stage atmospheric pressure thermo-catalytic plasma gasifier used in this apparatus and method may be sized to process from 5 to 24 metric tonnes per hour of mixed sources of organic waste and/or biomass, although gasifiers sized larger or smaller may be used; the exact throughput will depend on the composition of the feed material and the desired overall throughput of the generating plant.

This gasifier can be distinguished from other biomass plasma gasification reactor by the fact that it operates at about atmospheric pressure or slightly below atmospheric pressure and high temperature (greater than 1,200° C.) to ensure that there are no unconverted hydrocarbon molecules in the syngas product. In particular, the gasifier 10 is preferably operated at about atmospheric pressure (about 101325 Pa) or slightly below atmospheric pressure, which is typically up to about 500 Pa below atmospheric pressure and more typically about 200 Pa to about 500 Pa below atmospheric pressure. This one stage gasification process is unique since, as opposed to every other biomass gasification systems, it produces a syngas product free of tar that does not need to be processed in a secondary syngas cracking chamber.

In addition, the thermo-catalytic plasma gasification process is also unique in the sense that it makes it possible to continuously control and monitor the catalytic bed composition and height whose purpose is multifold. First, its constituents are typically mainly carbon, silica and calcium oxide to address specific gasification/vitrification process operating conditions.

Carbon is used, e.g. by means of coke, to ensure the plasma heat distribution across the cross-section of the reactor due to its high fixed-carbon content in contrast of the high volatile matter content of biomass. Silica and calcium oxide are used to maintain the proper and adequate lava pool chemistry prior to being tapped out of the reactor. These catalysts are continuously mixed together prior to being injected into the gasification reactor through a specific feeding system in such a way that the carbon to silica to calcium oxide ratio (C:SiO₂:CaO) optimizes the gasification operating conditions.

As shown in FIG. 2, gasifier 10 is constructed preferably of high-grade steel. The gasifier has a refractory lining 12 throughout its inner shell. Typically, the upper two-thirds of the gasifier is lined with up to four layers of refractory material and preferably three, with each layer about 4 to 6 inches thick or about 10 to 14 inches thick. Typically, the lower third of the gasifier is lined with up to four layers of refractory brick, and preferably three, for a total thickness of about 20 to 30 inches. Depending upon the application other refractory configurations may be used. Both sections utilize typical commercial refractory products, which are known to those in the reactor industry.

The gasifier 10 is shaped like a funnel and divided into three sections. The top third of the gasifier is referred to as the thermal cracking zone 16. Typically, gas exits the gasifier through a single outlet 30 in the center of the top of zone 16. Alternatively, a plurality of exit gas outlets may be provided around the top of zone 16.

Middle section 18 of the gasifier, also called the bed zone, is defined by a side wall 20 having a circumference smaller than that of zone 16. In the upper part of the section 18 and above the catalyst bed are two opposing feed biomass inputs 32 and 34, although a larger number may be provided. Typically the inputs 32 and 34 are located in the upper 50% and more typically in the upper 20% of section 18. Also the inputs 32 and 34 are typically at an angle of about 45 to about 90 degrees and more typically at an angle of about 60 to about 85 degrees relative to the vertical axis of the gasifier 10.

Section 18 is also encircled by two or more gaseous oxidant rings such as oxygen-enriched air or oxygen rings. Each ring injects, for example, oxygen-enriched air and/or oxygen in the bed zone (as pre-determined according to the biomass composition), through equally spaced inlets, called secondary tuyeres, 38 and 40. However, the most important fraction of enriched air or oxygen is injected under the bed zone through primary tuyeres, referenced as 39 and 41, which are typically made of water cooled copper. The number of primary tuyeres, which house non transferred plasma arc torches, typically ranges from two to six. The number of gas tuyeres may typically range from six to ten depending on the size of the gasifier and the throughput of the system, although a larger or smaller number may be used.

The number of rings may typically range from two to three depending on the catalyst and biomass bed height; although a larger or smaller number may be used.

Concerning the oxidant, nitrogen is considered an inert molecule in the syngas and therefore does not contribute to any process located downstream of the gasification reactor, including chemical synthesis or electricity production. Furthermore, the more nitrogen there is in the syngas—or inert to a further extent—the larger is the volume of syngas to process in subsequent systems.

As a consequence, since there is no commercially available system to remove nitrogen from syngas, large systems located downstream of the one stage thermo-catalytic gasification reactor would be needed to handle the syngas which therefore would raise the facility's capital expenditure.

Accordingly, since air is composed of primarily nitrogen (˜79% v/v) and oxygen to a lesser extent (˜21% v/v), air per se is not a preferred oxidant because an objective of the present disclosure is to reduce nitrogen content in the syngas. Similarly, enriched-air shall have sufficiently high oxygen content typically at least about 80% and more typically at least about 95% to be qualified as a viable oxidant agent. The table below provides a comparison of syngas composition and volume for two (2) different level of air enrichment.

Scenario 1 Scenario 2 Enriched air Enriched air composition composition N2 = 1%; N2 = 50%; O2 = 99% O2 = 50% Syngas 1,223 1,248 temperature (° C.) Syngas volume 30,535 36,531 (Nm³/hr) Syngas low heating 10,070 7,274 Value (kJ/kg) Syngas composition at reactor outlet (mol. % v/v) H₂O 16.40 15.74 CO 39.95 32.40 CO₂ 7.65 7.39 N₂ 3.23 19.11 H₂ 32.67 25.29

As expected, the volume of syngas is significantly decreased. In this particular example, it is decreased by 20% if the level of oxygen purity in the enriched air increases from 50% to 99%. In addition, the heating value of the syngas increases with the level of oxygen enrichment. In this particular example, the heating value increases by 40%.

In general, a level of oxygen purity equal to or greater than 95% v/v is preferred.

The bottom third of the gasifier is vitrification zone 19, which is defined by a side wall 22 having a circumference smaller than that of zone 18. Side walls 20 and 22 are connected by a frustoconical portion 24. Vitrification zone 19 houses one or more tap holes where molten slag liquid is tapped continuously typically into a refractory lined sand bin (not shown), where it is cooled into an inert slag material suitable for re-use as construction material. (Construction materials with which this slag may be used include tile, roofing granules, and brick.) This bottom section of the gasifier, which contains the molten slag, may, in certain configurations, be attached to the gasifier via a flanged fitting to enable rapid replacement of this section in the event of refractory replacement or repairs.

Each non transferred plasma arc torch plugged in primary tuyeres 39 and 41 is generally supplied with electric power, cooled deionized water and plasma gas through supply conduits from appropriate sources (not shown). The number of torches and primary tuyeres, the power rating of each torch, the capacity of the biomass feeding system, composition of the catalyst, the amount of catalyst, the oxygen-purity of the oxidant, the amount of oxidant, the size of the gasifier, the size and capacity of the syngas cooling, cleaning, compressing and conditioning systems are all variable to be determined according to the type and volume of biomass to be processed by the system. There are typically at least 3 and more typically at least 4 plasma torches around the circumference of the reactor 10.

The gasifier will typically contain throughout its shaft at intervals of about three feet or less, sensors to detect the pressure and temperature inside the gasifier, as well as gas sampling ports and appropriate gas analysis equipment at strategic positions in the gasifier to monitor the gasification process. The use of such sensors and gas analysis equipment is well understood in the art. See FIG. 4, which is an elevation partial view of gasifier 10 illustrating representative pressure sensors P3, P4 and P11 and temperature sensors T1, T2, TT4, T5, T6, T8, T9 and T10. Also, see FIGS. 5A-5C which are cross-sectional views of FIG. 4 illustrating location of representative pressure sensors P3, P7 and P11 and temperature sensors T1, T2, TT4, T5, T6, T8, T9 and T10. The nozzles of the sensors are spaced equidistantly around the circumference of the gasifier. The number of the nozzles of the sensors and types of sensors shown is for illustration purposes only.

Biomass and Biomass Feeding System

A compacting biomass delivery system operating through hydraulic cylinders and/or screws to reduce the biomass volume and to remove air and water in the biomass prior to feeding into the top of the bed zone as previously described and disclosed in the above identified Solena Fuels Corporation patents can be employed.

In order to accommodate biomass and biomass-residues, as per its definition by the UNFCC¹, organic renewable feed stocks biomass from multiple and mixed sources such as RDF (refuse-derived fuel), loose municipal solid waste (MSW), industrial biomass, and biomass stored in containers such as steel or plastic drums, bags and cans, a very robust feeding system can be used. Biomass may be taken in its original form and fed directly into the feeding system without sorting and without removing its containers. Biomass shredders and compactors capable of such operation are known to those of ordinary skill in the field of materials handling. Biomass feed may be sampled intermittently to determine its composition prior to treatment. ¹ http://cdm.unfccc.int/Reference/Guidclarif/mclbiocarbon.pdf

(a) Biomass means non-fossilized and biodegradable organic material originating from plants, animals and micro-organisms. This shall also include products, by-products, residues and waste from agriculture, forestry and related industries as well as the non-fossilized and biodegradable organic fractions of industrial and municipal wastes. Biomass also includes gases and liquids recovered from the decomposition of non-fossilized and biodegradable organic material. (b) Biomass residues means biomass by-products, residues and waste streams from agriculture, forestry and related industries.

In U.S. Pat. No. 6,987,792, it is mentioned that the compacting system shall be nitrogen purged. One of the reasons for having a nitrogen purged system, instead of air, is to avoid that the screw gets back-fired as it conveys feedstock towards the reactor. It is crucial that the system be purged with an inert gas, although not necessarily with nitrogen. The advantage of using nitrogen is that it is not expensive to produce. On the other hand, the main downside is that it increases the amount of nitrogen in the gas of synthesis (other sources of nitrogen are the air going through the plasma torch system and the nitrogen contained in the feedstock).

According to the present disclosure, an alternative to nitrogen as a purging agent is carbon dioxide. Although it will inevitably increase the amount of CO₂ in the syngas, off-the-shelf systems are commercially available to extract carbon dioxide from a syngas—unlike nitrogen—such as a Rectisol, Selexol or an amine unit. This alternative is particularly interesting in a scenario where a CO₂ removal unit would have to be used in any case, as it now provides a cheap alternative to decrease inert content in syngas.

All the biomass and organic material, including at times its containers, is crushed, shredded, mixed, compacted and pushed into the plasma reactor as a continuous block of waste by a system (not shown). The biomass can be comminuted to a preset size to insure optimal performance of the gasifier. The feeding rate can also be preset to ensure optimum performance of the gasifier.

Typically the organic material injected into the reactor has a physical size not less than about 2 cm in diameter to avoid pressure drop effect. Similarly, its size typically does not exceed 5 cm in diameter to ensure that the bed height does not exceed a specified maximum, thus limiting the height of the reactor's shaft.

For example, the pressure drop across the bed would be about 900 Pa/m if the particle size were 1 cm in diameter; whereas, it is only 10 Pa/m with a particle size of 5 cm in diameter. However, bed heights vary as a function of particle size and the bed height would be about 0.5 m if the particle size were 1 cm in diameter; whereas, it is 2.5 m with a particle size of 5 cm in diameter. Therefore, the overall pressure drop would be respectively 400 Pa and 25 Pa.

Therefore particle size and to a further extent pressure drop have significant impact on the design, and thus cost, of the induced draft located downstream of the reactor to extract the syngas. Consequently, the bigger the particle size is, the less pressure drop occurs, but the higher is the bed height. As shown in FIG. 3, it has been determined according to the present disclosure that the optimum particle size is about 3 to about 5 cm in diameter. Particle sizes exceeding 5 cm in diameter would certainly have as a consequence an increase in the height of the shaft of the reactor.

The blocks of biomass are delivered into the gasifier continuously from multiple locations in zone 18 of the gasifier, ensuring even distribution in the gasifier until a specific biomass bed height is achieved above the consumable catalyst bed. Two blocks of biomass may be fed simultaneously into input chutes provided at diametrically opposite sides of gasifier 10. More than two chutes may be provided to accept additional blocks. Any arrangement is suitable, so long as it avoids an uneven build-up of biomass in any one location in zone 18 of the gasifier.

The lifetime of the refractory materials and thus the reactor operating conditions as well are enhanced by injecting the organic feedstock into the upper part of the bed zone 18 instead of upper section 16 of the gasifier.

In addition, for reliability purposes, a reactor should typically house at least two (2) feeding systems for the biomass feedstock and at least one (1) feeding system for the catalyst material. This is due to the fact that catalyst material cannot be compacted with biomass material due to their different densities.

Pressure sensors and temperature sensors along the gasifier, as well as microwave sensors on top of the gasifier, can be used to measure bed height and control the feeding rate of the biomass. As a back-up, sight ports may be provided at certain locations to verify activities inside the gasifier. All information from the sensors will be fed into a digital control system (DCS) that coordinates the operation of the whole plant performance. The coordination and monitoring of the feeding system through the use of sensors and a DCS as part of the process control of the gasifier are normal protocol and readily apparent to those skilled in the art.

Alternate configurations of the feeding system may be used for different materials. For instance, fine powders or liquid biomass may be injected directly into the gasifier. Gas transport may be used for fine solids, such as coal fines. Standard pumps may be used for liquids. Such systems are well known to practitioners of material handling.

Operation of the SPGV Reactor

The shredded and compacted biomass material 58 is fed by the feeding system continuously into gasifier 10. For the sake of simplicity, the continuous feeding from opposite sides of the gasifier ensures uniform distribution of the biomass feed across the cross section of the gasifier. The uniformity of the biomass feed distribution as it forms a biomass bed ensures the uniform, upward flow of hot gas from the plasma heated catalyst bed. The catalyst bed toward the bottom of the plasma gasifier is constantly heated by the plurality of plasma torch plumes uniformly distributing the heated gas and feedstock particles upward across the cross section of the gasifier. The heat and hot gas when distributed uniformly upward, heat and dry the down-flowing biomass feed and enable the gasification processes to occur efficiently. The uniform heat distribution upward and the presence of the catalysis bed also avoids channeling of the heat, which in turn prevents the bridging of the biomass feed, which is a typical problem encountered in other thermal biomass treatment processes.

The gasifier's funnel shape and the rising gas feed rate (from the torches and other gas inlets) are designed to ensure minimum superficial velocity of the rising hot gases. This low superficial velocity allows the entering biomass feed to descend into the biomass bed completely and not be forced upward into the exiting gas as unprocessed biomass or particulate carryover. Additionally, the cracking zone 16 of the gasifier serves to ensure that all hydrocarbon materials are exposed to the high temperature with residence time in excess of 2-3 seconds prior to exiting the gasifier. This zone completes the thermal cracking process and assures complete gasification and conversion of higher hydrocarbons to CO and H₂.

As the cold waste feeds are continuously fed into the one stage thermo-catalytic plasma gasifier and form a bed of biomass on top of a previously heated bed of consumable catalyst in the bottom of the gasifier, the descending cold waste and the rising heated gas from the consumable catalyst bed create a counter-current flow that allows the complete pyrolysis/gasification of the biomass uniformly across the reactor.

The consumable catalyst bed applied and used in this process is not unlike that used in typical metallurgical blast furnaces, and its inclusion into the gasification process serves at least the following several functions: (1) it allows for the distribution of the plasma-generated heat uniformly across the plasma gasifier and thus prevents the excessive wear and tear in the refractory that is normally encountered when intense focal heat sources such as plasma torches are utilized; (2) it initiates the gasification reaction by providing the key component of the exit gas, i.e., the CO (carbon monoxide) contributing to the heating value of the exit top gas; (3) it provides a porous but solid support framework at the bottom of the gasifier upon which the biomass bed can be deposited; (4) it allows the hot gaseous molecules to move upward into and through the biomass bed uniformly, while allowing the inorganic material in the biomass such as metal and ferrous to be melted and to flow downward into the molten pool at the bottom of the gasifier; and (5) it provides a layer of protection inside the innermost refractory layer and thus decreases heat loss in the gasifier while extending the refractory life.

In addition, the catalytic bed composition and height, whose purpose is multifold, are continuously controlled and monitored. First, its constituents are typically mainly carbon, silica and calcium oxide to address specific gasification/vitrification process operating conditions. Carbon is used, by means of coke, to ensure the plasma heat distribution across the cross-section of the reactor due to its high fixed-carbon content in contrast of the high volatile matter content of biomass. Silica and calcium oxide are used to maintain the proper and adequate lava pool chemistry prior to being tapped out of the reactor. These catalysts are continuously mixed together prior to being injected into the gasification reactor through a specific feeding system in such a way that the carbon to silica to calcium oxide ratio (C:SiO₂:CaO) optimizes the gasification operating conditions.

The bed of catalyst is maintained by injecting catalyst typically at a rate of about 2% to about 10%, and more typically about 3% to about 5% of the biomass weight rate. It is constantly consumed at a slower rate than is the biomass bed due to its higher density fixed carbon content than biomass, higher melting temperature, and hard physical properties. The height of the consumable catalyst bed, like the biomass bed, is monitored constantly via temperature and pressure sensors located circumferentially around the gasifier and at various elevations along the shaft. As biomass bed and catalyst bed 70 are consumed during the process, the sensors will detect a temperature and pressure gradient across the gasifier and automatically trigger the feeding system to increase or decrease the bed height in a steady-state operation in order to maintain the optimum syngas power.

The interaction of a catalysis bed and molten material is a well-understood phenomenon. In the case of molten metal flowing over hot coke, as in the case of foundry cupola melters, the molten iron does not stick to the hot bed but flows over it. The same phenomenon is observed during the melting of non-metallic material, i.e., vitrification of slag. Unlike metal melting, slag vitrification does not involve dissolution of carbon since the solubility of carbon from the coke into the molten slag is negligible.

The hydrocarbon portion of the biomass will be gasified under the partially reducing atmosphere of the gasifier in an oxygen-deprived (with respect to complete oxidation of carbon to CO₂) environment. Therefore, there is no combustion process occurring in the gasifier to produce the pollutants normally expected from incinerators, such as semi-volatile organic compounds (SVOCs), dioxins, and furans, which are carcinogenic compounds.

The controlled introduction of oxygen and/or oxygen-enriched air and/or steam into the plasma gasifier to generate a controlled partial oxidation reaction of gasification will generate an exit top syngas with higher calorific content while reducing the specific energy requirement, that is, the energy consumed by the plasma torches to gasify the biomass. This in turn results in a higher net energy production from the gasification of organic biomass.

The biomass bed is continuously reduced by the rising hot gases from the consumable catalyst bed and continuously replenished by the feeding system in order to maintain the bed height. This sequence results in a temperature gradient from at least about 3000° C. at the bottom of the gasifier to at least about 1200° C. in the exit syngas outlet. The rising counter-current system thus established serves to dry the incoming biomass and thus allow the system to handle a biomass stream with moisture content of up to 90% in the case that high moisture biomass is used without causing shutdown as in other thermal combustion system. Naturally, the high moisture content of the biomass feed would result in a syngas with lower heating value due to the lower hydrocarbon content of the biomass feed.

The gasifier typically operates at about atmospheric pressure or more typically slightly below atmospheric pressure due to the exit gases being constantly extracted out of the gasifier, for instance, by an induction fan (ID fan) or blower (not shown). As mentioned previously, the gasifier conditions are reducing to partial oxidation in nature, with mostly limited oxygen conditions suitable for the gasification process. The independent control variables of the process are (1) the biomass feed rate, (2) the consumable catalyst bed height, (3) the torch power, (4) the oxidant gas flow, and (5) the C:SiO₂:CaO mixing ratio of catalyst material considered in the process.

The molten, pool of inorganic material at the bottom of gasifier 10 is tapped continuously out of the gasifier via slag tap 37 into refractory-lined sand boxes and cast into large blocks to maximize volume reduction.

To ensure that the slag flow is uniformly constant and to prevent plugging of the slag tap hole 37, the temperature of the slag as reflected in the temperature of the gasifier bottom thermocouple system as well as the slag viscosity may be independently controlled by the plasma torch power and the amount of C:SiO₂:CaO catalyst added through known relations. Lava pool height is also measured by the use of thermal sensors.

All these monitored parameters regarding the temperature, pressure, gas composition, and flow rates of gas and molten material are fed as inputs into a computerized DCS system, which in turn is matched to process controls of the independent variables such as torch power, air/gas flow, biomass and catalyst feed rates, etc.

Depending on the previously analyzed waste feed, specific gasification and vitrification conditions are predetermined and parameters pre-set by the DCS control system. Additional and optimizing conditions will be generated and adjusted during start-up of operation when actual biomass materials are fed into the system.

Operating Principles

In general, the plasma gasification-vitrification apparatus and process described herein functions and operates according to several main principles.

Variations in the biomass feed will affect the outcome of the process and will require adjustment in the independent control variables. For example, assuming a constant material feed rate, a higher moisture content of the biomass feed will lower the exit top syngas temperature; the plasma torch power must be increased to increase the exit syngas temperature to the set point value. Also, a lower hydrocarbon content of the biomass will result in reduction of the carbon monoxide and hydrogen content of the exit gas resulting lower high heating value (HHV) of the exit top syngas; the enrichment factor of the inlet gas and/or plasma torch power must be increased to achieve the desired HHV set point. In addition, a higher inorganic content of the biomass will result in an increase in the amount of slag produced resulting in increased slag flow and decreased temperature in the molten slag; the torch power must be increased for the slag temperature to be at its target set point. Thus, by adjusting various independent variables, the gasifier can accommodate variation in the incoming material feed while maintaining the desired set points for the various control factors.

Start-Up

The goal of a defined start-up procedure is to create a gradual heat up of the plasma gasifier to protect and extend the life of the refractory and the equipment of the gasifier, as well as to prepare the gasifier to receive the biomass feed material. Start-up of the gasifier is similar to that of any complex high-temperature processing system and would be evident to skilled artisans in the thermal processing industry once aware of the present disclosure. The main steps are: (1) start the gas turbine on natural gas to generate electricity; (2) gradually heat up the gasifier by using a natural gas burner (this is done primarily to maximize the lifetime of the refractory material by minimizing thermal shock) and switch to plasma torches once suitable inner temperatures are reached; and (3) start the syngas clean-up system with the induced draft fan started first. The consumable catalyst bed 70 is then created by adding the material such that a bed is formed. The bed will initially start to form at the bottom of the gasifier, but as that initial catalyst, which is closest to the torches, is consumed, the bed will eventually be formed as a layer above the plasma torches at or near the frustoconical portion 24 of the gasifier.

Biomass or other feed materials can then be added. For safety reasons, the preferred mode of operation is to limit the water content of the biomass to less than 5% until a suitable biomass bed is formed. The height of both the consumable catalyst bed and the operating biomass bed depends upon the size of the gasifier, the physico-chemical properties of the feed material, operating set points, and the desired processing rate. However, as noted, the preferred embodiment maintains the consumable catalyst bed above the level of the plasma torch inlets.

Steady-State Operation

When both the biomass bed and the catalyst bed reach the desired height, the system is deemed ready for steady operation. At this time, the operator can begin loading the mixed waste feed from the plant into the feeding system, which is set at a pre-determined throughput rate. The independent variables are also set at levels based on the composition of the biomass feed as pre-determined. The independent variables in the operation of the SPGV gasifier are typically:

A. Plasma Torch Power

B. Gas Flow Rate

C. Gas Flow Distribution

D. Bed Height of the Biomass and Catalyst

E. Feed Rate of the Biomass

F. Feed Rate of the Catalyst

During the steady state, the operator typically monitors the dependent parameters of the system, which include:

A. Exit Top Gas Temperature (measured at exit gas outlet)

B. Exit Top Gas Composition and Flow Rate (measured by gas sampling and flow meter at outlet described above)

C. Slag Melt Temperature and Flow Rate

D. Slag Leachability

E. Slag Viscosity

During operation and based on the above described principles, the operator may adjust the independent variables based upon fluctuations of the dependent variables. This process can be completely automated with pre-set adjustments based on inputs and outputs of the control monitors of the gasifier programmed into the DCS system of the plasma gasifier and the whole plant. The pre-set levels are normally optimized during the plant commissioning period when the actual biomass feed is loaded into the systems and the resultant exit top gas and slag behavior are measured and recorded. The DCS will be set to operate under steady state to produce the specific exit gas conditions and slag conditions at specified biomass feed rates. Variations in feed biomass composition will result in variations of the monitored dependent parameters, and the DCS and/or operator will make the corresponding adjustments in the independent variables to maintain steady state.

Cooling and Scrubbing of the Exit Top Gas from the Plasma Gasifier

As mentioned above, one objective for the operation of the SPGV system is to produce a syngas with specific conditions (i.e., composition, calorific heating value, purity and pressure) suitable for feeding into a plurality of industrial applications, including but not limited to gas turbine for production of renewable electrical energy, Fischer-Tropsch synthesis for production of transportation liquid fuels, combined heat and power system for production of district heat and electricity, chemical industry system, etc.

Because the syngas is generated by the pyrolysis/gasification of organic biomass material through the process described herein, there will exist certain amounts of biomass impurities, particulates and/or acid gases which are not suitable to the normal and safe operation of these systems. Procedures to clean the exit gas are described in the above mentioned Solena patents.

Exemplary embodiments of the present disclosure include:

Embodiment 1

An apparatus for one stage thermo-catalytic plasma gasification and vitrification of organic material comprising: a generally funnel-shaped reactor having an upper section and a lower section, said lower section comprising a first, wider portion connected by a frustoconical transition to a second, narrower portion, and being suitable to receive a catalyst bed, and said upper section having at least one gas exhaust port; a plurality of inlets for said material from a plurality of directions located at the upper part of said lower section for introducing said material into said upper portion of said lower section; a gas inlet system disposed around said lower section to provide gas into said lower section through one or more intake ports in said lower section; and a plurality of plasma arc torches mounted in said lower section to heat said catalyst bed and said organic material.

Embodiment 2

An apparatus according to Embodiment 1, further comprising: a material delivery system to provide said material to said reactor through said plurality of intake ports, said delivery system comprising: a receptacle to receive said material, a shredding and compacting unit disposed to accept said material from said receptacle and to shred and compact said material, and a transfer unit to deliver said shredded and compacted material to said reactor.

Embodiment 3

An apparatus according to Embodiment 2 wherein said material comprises carbonaceous material.

Embodiment 4

An apparatus according to Embodiment 3 wherein said organic material comprises the non-fossilized and biodegradable organic material originating from products, by-products and residues of plants, municipal solid waste, agriculture waste, forestry waste and their related industries.

Embodiment 5

An apparatus according to any one of Embodiments 3 or 4 wherein said catalyst bed is about 1 meter in height.

Embodiment 6

An apparatus according to any one of Embodiments 2-5 further comprising a plurality of sensors disposed throughout said reactor to sense one or more of: a height of said catalyst bed, a height of a bed of said organic material, a temperature of said reactor, a flow rate of gas in said reactor, and a temperature of a syngas exhausted from said reactor through said exhaust port.

Embodiment 7

An apparatus according to any one of Embodiments 1-6 wherein said lower section has one or more tap holes at a bottom thereof.

Embodiment 8

A method for the conversion of organic material by plasma gasification and vitrification, said method comprising: providing a catalyst bed in a lower section of a reactor; providing one or more successive quantities of said material from a plurality of directions into an upper part of a lower section of a reactor, said upper section having at least one gas exhaust port connected to a fan, said material forming a bed atop said catalyst bed; heating said catalyst bed and said biomass material bed using a plurality of plasma arc torches mounted in said lower section; and introducing into said lower section a gaseous oxidant.

Embodiment 9

The method according to Embodiment 8 wherein said catalyst bed comprises carbon, silica and calcium oxide.

Embodiment 10

The process according to any one of Embodiments 8 or 9, wherein said gaseous oxidant comprises oxygen-enriched air or oxygen.

Embodiment 11

The process according to Embodiment 10, wherein said oxygen-enriched air comprises at least about 80% (v/v) of oxygen.

Embodiment 12

The process according to Embodiment 10, wherein said oxygen-enriched air comprises at least about 95% (v/v) of oxygen.

Embodiment 13

The process according to any one of Embodiments 8-12, wherein said organic material has a particle diameter size of about 2 cm to about 5 cm.

Embodiment 14

The process according to any one of Embodiments 8-13, wherein said organic material has a particle diameter size of about 3 cm to about 5 cm.

Embodiment 15

The process according to any one of Embodiments 8-14, wherein the temperature in the catalyst bed in the lower section is greater 3000° C.

The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “having” or “including” and not in the exclusive sense of “consisting only of” The terms “a” and “the” as used herein are understood to encompass the plural as well as the singular. The term “atmospheric pressure” as used herein refers to atmospheric pressure (about 101325 Pa) and pressure below atmospheric pressure, wherein slightly below is typically up to about 500 Pa below atmospheric pressure and more typically about 200 Pa to about 500 Pa below atmospheric pressure.

All publications, patents and patent applications cited in this specification are herein incorporated by reference, and for any and all purpose, as if each individual publication, patent or patent application were specifically and individually indicated to be incorporated by reference. In the case of inconsistencies, the present disclosure will prevail.

The foregoing description of the disclosure illustrates and describes the present disclosure. Additionally, the disclosure shows and describes only the preferred embodiments but, as mentioned above, it is to be understood that the disclosure is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the concept as expressed herein, commensurate with the above teachings and/or the skill or knowledge of the relevant art.

The embodiments described hereinabove are further intended to explain best modes known of practicing it and to enable others skilled in the art to utilize the disclosure in such, or other, embodiments and with the various modifications required by the particular applications or uses. Accordingly, the description is not intended to limit it to the form disclosed herein. Also, it is intended that the appended claims be construed to include alternative embodiments. Each of the claims defines a separate invention, which for infringement purposes is recognized as including equivalents to the various elements or limitations specified in the claims.

Various terms have been defined above. To the extent a term used in a claim is not defined above, it should be given the broadest definition persons in the pertinent art have given that term as reflected in at least one printed publication or issued patent. Furthermore, all patents, test procedures, and other documents cited in this application are fully incorporated by reference to the extent such disclosure is not inconsistent with this application and for all jurisdictions in which such incorporation is permitted. 

What is claimed is:
 1. An apparatus for one stage thermo-catalytic plasma gasification and vitrification of organic material comprising: a generally funnel-shaped reactor having an upper section and a lower section, said lower section comprising a first, wider portion connected by a frustoconical transition to a second, narrower portion, and being suitable to receive a catalyst bed, and said upper section having at least one gas exhaust port; a plurality of inlets for said material from a plurality of directions located at the upper part of said lower section for introducing said material into said upper portion of said lower section; a gas inlet system disposed around said lower section to provide gas into said lower section through one or more intake ports in said lower section; and a plurality of plasma arc torches mounted in said lower section to heat said catalyst bed and said material.
 2. An apparatus according to claim 1, further comprising: a material delivery system to provide said material to said reactor through said plurality of intake ports, said delivery system comprising: a receptacle to receive said material, a shredding and compacting unit disposed to accept said material from said receptacle and to shred and compact said material, and a transfer unit to deliver said shredded and compacted material to said reactor.
 3. An apparatus according to claim 2 wherein said material comprises biomass material.
 4. An apparatus according to claim 3 wherein said biomass material comprises the non-fossilized and biodegradable organic material originating from products, by-products and residues of plants, municipal solid waste, agriculture waste, and forestry waste.
 5. An apparatus according to claim 5 wherein said catalyst bed is about 1 meter in height.
 6. An apparatus according to claim 2 further comprising a plurality of sensors disposed throughout said reactor to sense one or more of: a height of said catalyst bed, a height of a bed of said material, a temperature of said reactor, a flow rate of gas in said reactor, and a temperature of a gas exhausted from said reactor through said exhaust port.
 7. An apparatus according to claim 1 wherein said lower section has one or more tap holes at a bottom thereof.
 8. A method for the conversion of organic material by one stage atmospheric thermo-catalytic plasma gasification and vitrification, said method comprising: providing a catalyst bed primarily composed of carbon, silica and calcium oxide in a lower section of a reactor; providing one or more successive quantities of said material from a plurality of directions into an upper part of a lower section of a reactor, said upper section having at least one gas exhaust port connected to a fan, said material forming a bed atop said catalyst bed; heating said catalyst bed and said material bed using a plurality of plasma arc torches mounted in said lower section; and introducing into said lower section a gaseous oxidant.
 9. The method according to claim 8 wherein said catalyst bed comprises carbon, silica and calcium oxide.
 10. The process according to claim 8, wherein said gaseous oxidant comprises oxygen-enriched air or oxygen.
 11. The process according to claim 10, wherein said oxygen-enriched air comprises at least about 80% (v/v) of oxygen.
 12. The process according to claim 10, wherein said oxygen-enriched air comprises at least about 95% (v/v) of oxygen.
 13. The process according to claim 8, wherein said organic material has a particle diameter size of about 2 cm to about 5 cm.
 14. The process according to claim 8, wherein said organic material has a particle diameter size of about 3 cm to about 5 cm.
 15. The process according to claim 8, wherein the temperature in the carbon catalyst bed in the lower section is greater 3000° C. 